Over the years, there have been developed a number of proposals for scroll compressors which quite frequently are employed as the compressor element in a refrigerating system. Typically, such compressors include two so-called scroll elements which are generally in the form of facing plates each provided with a helical vane. The vanes on each plate interfit with each other to define one or more closed pockets by points of contact between the vanes on the two plates.
The vanes on one of the plates is made to orbit with respect to the vane on the other so that the pocket or pockets travel from an inlet to an outlet and typically progressively become reduced in size to compress the fluid.
There are two general forms of such compressors. Each, in addition to the foregoing characteristics possesses unique characteristics of its own. For example, one of the two types provides for continuous rotation, in synchronism, of both scroll elements in addition to the relative orbital motion. This approach is exemplified, for example, in Thelen et al. U.S. Pat. No. 4,178,143 issued Dec. 11, 1979.
In the other form of such a compressor, both scroll members are fixed against rotation, although one is allowed to orbit with respect to the other as mentioned previously. This approach is exemplified in, for example, Terauchi et al. U.S. Pat. No. 4,332,535 issued June 1, 1982 and by Kousokabe U.S. Pat. No. 4,343,599 issued Aug. 10, 1982.
Regardless of the approach employed, because of the relative movement between the scroll elements and the fact that near contact between the vanes thereof is required to produce the closed pocket necessary to convey and compress the working fluid, it is highly desirable to lubricate the interface of the two scrolls to minimize wear which, amongst other things, would lead to leakage paths thereby lowering efficiency of the operation of the device. Consequently, it is desirable to introduce a lubricant into the working fluid stream at or about the time it enters the scroll compressor or earlier and an example of such is shown in the previously identified Kousokabe patent. This lubricant serves the desirable function of lubrication to avoid wear and in addition, improves sealing between the scroll members at their points of near contact to increase operational efficiency.
At the same time, it is not particularly desirable to allow the lubricant to exit the compressor to the point where it enters the remainder of the refrigeration system. The lubricant typically will impede heat transfer in heat exchange coils utilized in such systems and, dependent upon the configuration of the plumbing in such a system, may be trapped and therefore unable to return to the compressor to provide the necessary lubrication. This difficulty is likewise recognized by Kousokabe who provides two different schemes for removing the lubricant from the compressor effluent before it can enter the remainder of the system with which the compressor is used. In both cases, Kousokabe utilizes a suction scheme to introduce lubricant into the compressor adjacent its inlet. In one case, the suction system is internal to the compressor housing while in another it is external. The latter is obviously to be avoided since the nature of the system is such it can be easily damaged. Moreover, compactness is sacrificed. In either case, a suction system is not particularly desirable because of the limitation on pressure differentials obtainable which in turn means that the system may be easily clogged and cannot be cleared readily due to such low pressure differential.
As regards removal of lubricant, in one embodiment, Kousokabe utilizes an external cyclone separator. Such a system, while functional, is undesirable in that bulk of the overall compressor is considerably increased and again, there are sensitive components external of the compressor housing which may be easily damaged. In another system, Kousokabe directs output of the compressor against a chamber wall. Presumably, the liquid lubricant agglomerates on such wall and flows to a reservoir by dripping down such wall while the compressed fluid exits through an outlet from the chamber which is so disposed as to prevent entry of lubricant thereinto. The difficulty with this approach is that a fine mist of lubricant may still exist within the chamber and exit the fluid outlet. Such a fluid mist may agglomerate elsewhere in the system and pose the difficulties mentioned previously.
The present invention is directed to overcoming one or more of the above problems.